IR images, sometimes referred to as thermal images if the IR radiation information on which the image is based is within the thermal spectrum, of systems that include electrical and mechanical devices and structures are useful for monitoring and analyzing the performance thereof, both during design and development for design optimization purposes, and during operational service for inspection and maintenance purposes.
An IR or thermography arrangement or imaging device, that may in embodiments be in the form of a camera, is typically provided with a visual light (VL) imaging system configured to capture a VL image, an IR imaging system configured to capture an IR image, and a processor configured to process the captured IR image and the captured VL image into a combined image. Combination methods known in the art include e.g. fusion, blending/alpha-blending, picture-in-picture and temperature thresholding, or combinations of said methods. The use of combined IR/VL images is advantageous as it enables analysis and identification of variations in temperature in an object using IR data from the IR image while at the same time displaying enough data from the VL image to simplify orientation and recognition of objects in the resulting image for a user using the imaging device.
A variety of methods for presenting a thermal image combined with a corresponding visible light image exists, wherein an IR image may e.g. be moved, resized and reshaped inside a visible light image. There is still a need for new methods for presenting thermal images that can improve the ease of viewing and interpreting the thermal images. Attempts have been made to combine and mix pixels, a process sometimes referred to as fusion or blending, from the IR image and the visible light image of the same scene. One example of prior known techniques of mixing is changing the visible content of an image by either strictly selecting visible light image data for the pixel representation or strictly selecting IR image data dependent on whether the measured or calculated temperature value associated with the respective pixel is above or below a preset threshold of current temperatures of a scene. When a temperature threshold or interval is changed, the pixels of the image are globally reassigned to represent VL or IR image data dependent on the new temperature thresholds or intervals. The IR image data may be in grey scale or in color, according to assignment of color and/or grey scale values according to mapping to a preset palette. This assignment of pixel values is commonly referred to as pseudo coloring. For many user applications the connection between color/grey scale levels and temperatures is essential in the interpretation of IR or combined IR/VL, image data. Color or grey scale information in the image that draws an observer's attention while not representing information of interest therefor hinders the observer from correctly interpreting the information and correctly analyzing the imaged scene.
There is a need for providing visually improved images that makes it easier for an observer to interpret the content of the imaged scene.